Kinetic analysis of sinter-crystallization of mullite and cristobalite from kaolinite

A non-isothermal kinetic analysis of high-temperature processes occurring during thermal treatment of kaolinite is performed by the thermodilatometric analysis. The measurements are carried out using the horizontal push-rod dilatometer on compact samples with heating rates from 1 to 10 °C min–1 in dynamic N2 atmosphere. For the parameterization of thermodynamically stable phases such as mullite and cristobalite, the Kissinger method is used. The obtained value of apparent activation energy for sinter-crystallization of mullite is (726 ± 9) kJ mol–1 and the thickening of long mullite needles is determined as a mechanism of this process. The results also show that the apparent activation energy for sinter-crystallization of cristobalite is (565 ± 38) kJ mol–1.